libwebp: update snapshot to v0.3.0-rc6

third_party/libwebp/utils/quant_levels.c

 // Copyright 2011 Google Inc. All Rights Reserved.
 //
 // This code is licensed under the same terms as WebM:
 //  Software License Agreement:  http://www.webmproject.org/license/software/
 //  Additional IP Rights Grant:  http://www.webmproject.org/license/additional/
 // -----------------------------------------------------------------------------
 //
 // Quantize levels for specified number of quantization-levels ([2, 256]).
 // Min and max values are preserved (usual 0 and 255 for alpha plane).
 //
@@ skipping 122 matching lines @@
       data[n] = map[data[n]];
     }
   }
  End:
   // Store sum of squared error if needed.
   if (sse != NULL) *sse = (uint64_t)err;
 
   return 1;
 }
 
-int DequantizeLevels(uint8_t* const data, int width, int height) {
-  if (data == NULL || width <= 0 || height <= 0) return 0;
-  // TODO(skal): implement gradient smoothing.
-  (void)data;
-  (void)width;
-  (void)height;
-  return 1;
-}
-
 #if defined(__cplusplus) || defined(c_plusplus)
 }    // extern "C"
 #endif